1. Field of the Invention
This invention relates to an improvement on a device for detecting the size of the original placed on the copy board in the copying machine.
2. Description of the Prior Art
In the conventional copying machines, such as those proposed in the Japanese patent application Laid Open No. 11,242/1975, an appropriate size of copying paper is selected from among different sizes of paper or, the rolled copying paper is cut to the appropriate size according to the size of the original. The device for detecting the size of the original or the material to be copied in such copying machines comprises a light emitting member and a photoelectric conversion member, provided on the platen cover and on the underside of the copy board, respectively, along the diagonal line of the copy board so that they face each other. The size of the original is determined from the information derived from the photoelectric conversion member.
This kind of original size detection device has the disadvantage that the variation of sensitivity of the photoelectric conversion member, the variation and fluctuation of intensity of the light irradiated from the light emitting member, and external light leaking in through the gap of the platen cover are likely to result in the photoelectric conversion member or device erroneously detecting the size of the original.
Furthermore, since either the light emitting member or the photoelectric conversion member is provided to the platen cover which is opened or closed when the original is set on or taken from the copy board, the member on the platen cover is liable to trouble and the shadow of the light emitting member or the photoelectric conversion member located on the outside of the original may be printed on the transfer paper.